Skip to main content

Full text of "Handbook Of Chemical Engineering - I"

See other formats


80
CHEMICAL ENGINEERING
dered. The boiler and engine, or the operating motor, boom, hoisting drums, clutches, brakes, etc., are mounted on a turntable supported by the body of the crane—the engine or motor also actuating the propelling mechanism for moving the crane.
Locomotive cranes are ordinarily rated as of 10-, 15-, 20-, 25- or 30-ton lifting capacity, but such rating is misleading as it designates the ultimate lifting power of the crane with its boom elevated at a steep angle and a lifting radius of 12 or 13 ft. As the boom is lowered and the lifting radius increased, the capacity of the crane— its lifting power—drops rapidly, so that a small crane with a short lifting radius will handle a greater load than a considerably larger crane with a long lifting radius. Table 1 lists the lifting capacities of standard locomotive cranes in tons (2,000 Ib.) for various lifting radii, from which the weight of the bucket, shovel or magnet should be deducted to arrive at the effective capacity of the crane. Table 2 gives the average weights of the standard sizes of clam-shell and orange-peel buckets ordinarily employed.
TABLE   1.—LIFTING  CAPACITY  OF  STANDAKD   LOCOMOTIVE   CRANES
Lifting radius, feet	Size — rated capacity in tons				
	10	15	20	25	30
12-13	10.0	15.0	20.0	25.0	30.0
15	8.6	12.0	16.3	19.0	23.0
20	5.8	8.6	11.3	13.5	15.8
25	4.3	6.8	8.9	10.4	12.0
30	3.5	5.3	7.0	8.3	9.6
35	3.0	4.5	5.8	7.0	7.9
40	2.3	3.8	4.9	5.8	6.7
45	2.0	3.3	4.2	5.0	5.7
50	1.6	2.8	3.7	4.3	4.9
55	1.4	2.4	3.2	3.8	4.3
60	1.2	2.0	2.8     j       3.3		3.7
TABLE 2.—AVERAGE WEIGHT or STANDARD BUCKETS
Type	Size, cubic	Weight,	Type	Size, cubic	Weight,
	yards	pounds		yard	pounds
Clam-shell . . .	H	2,200	Orange-peel..	H	3,800
	i	2,800		1	4,800
	ilA	3,800		\1A                  7,100	
	2			2                      9 , 500	
Rarely is it possible to foretell the maximum proportional lifting radius at which a locomotive crane may be called upon to work, so considerable leeway in capacity must be allowed. The desired tonnage should be known, so a convenient empirical Formula (1) follows for ascertaining the size of crane best suited under ordinary conditions, while Formula (2) gives the average capacity of standard locomotive cranes in tons per hour when handling loose material.